2017 was Steam's best year yet in terms of revenue.
Steam revenue in 2017 is estimated to have hit $4.3 billion, half of which can be attributed to just 100 titles out of the over 21,000 available on the service.
Speaking during a GDC 2018 panel, SteamSpy's Sergey Galyonkin said the $800 million revenue increase over 2016's $3.5 billion made 2017 Steam's biggest year yet. And the $4.3 billion in revenue doesn't take into account sales of DLC, in-app purchases or microtransactions.
Out of the over 21,000 titles available on the Steam service (7,696 were released in 2017), the biggest earner was PlayerUnknown's Battlegrounds. According to Galyonkin's estimates, PUBG has been purchased by 28 million Steam users,generating $600 million in revenue (thanks, Gamasutra).
The second best-selling game in 2017 was Counter Strike: Global Offensive with $120 million in revenue, followed by GTA 5 with $83 million.
According to Galyonkin, a game needs to have sold $22 million in order to hit the top 20 on the service. Of those in the current top 20, seven were released before 2017 and include The Witcher 3, Dark Souls 3, Rainbow Six Siege and others, via GI.biz.
Steam also saw an increase in users during 2017. Galyonkin said there are currently 291 million Steam accounts, and 63 million were created just last year. In the last two weeks, 57 million players were active, and 25% of all users have played a game during the same time period.
The rise in users Galyonkin attributed to cyber cafes in China where PUBG is a huge hit.